Sea levels are rising because of climate change

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Background - 4 July, 2012

Sea level rise due to global warming is a serious threat, on collision course with large and growing coastal populations. For some people living in low-lying coastal areas and on small islands, damage from sea level rise is already a daily reality. Greenpeace is fighting to limit future sea level rise with an urgent shift to 100 percent safe, clean renewable energy.

Why are sea levels rising?

The main cause of sea level rise today is global warming caused by human activity. This warming drives sea level rise in two main ways:

by warming ocean water; as it warms, water expands, taking up more space

by melting land-based ice (glaciers and ice sheets), sending more water to our oceans.

Sea level rise past, present and future

So far sea levels have risen by about 20cm (since 1880). As global warming continues, the rate is speeding up, with sea levels currently rising at about 3mm per year.

Looking ahead, future sea level rise could total one meter or even more by the end of this century if emissions are not held in check.

Why is sea level rise dangerous?

Sea level rise has already worsened flooding caused by tropical cyclones and everyday high tides. Yet today about half of the world's population — three billion people — live within 200km of a coastline.

These coastal populations are growing and urbanising faster. People and infrastructure are crowding into vulnerable coastal areas. Most mega-cities are in coastal zones. Rising sea levels could inundate low-lying coastal areas unless cities spend billions to keep ocean waters at bay.

Water contamination, erosion and storm damage

Rising seas can send ocean water further inland. When this salt water contaminates it, fresh groundwater becomes useless for drinking or farming.

As waves reach higher and further, they cause more erosion damage on coastal lands. This damage becomes even worse during storms, when seawater and waves push still further inland, damaging more wildlife habitat, soil, buildings, and roads and other infrastructure.

Small island nations on the front line

People of small island nations are among the first and worst affected by sea level rise and climate change. Some small islets among the Pacific islands of the Republic of Kiribati have already disappeared beneath the rising ocean. Today, flooding on Kiribati regularly kills crops, contaminates drinking water, and floods homes.

Between 1.2 and 2.2 million people could displaced from the Caribbean and Indian and Pacific ocean islands with future sea level rise of between 0.5 and 2m (under 4° Celsius of warming).

What can be done about sea future level rise?

We cannot avoid some amount of future sea level rise. This is because emissions already in the atmosphere will "lock in" some future warming and sea level rise.

But the choices we make today and tomorrow will have a big effect on how much and how fast sea level rises beyond 2050.With strong cuts to emissions, future sea level rise could be kept to between 28 and 61cm.

What is Greenpeace doing?

We know future sea level rise depends on what we do now. That's why Greenpeace is driving an urgent shift away from the polluting and dangerous energy systems that fuel global warming and sea level rise. We are helping make the leap to a safe, secure energy system 100 percent powered by the sun, wind, and other clean, renewable sources.

We also believe it's time to hold big carbon polluters to account, and that big polluters should contribute to making at-risk communities more resilient in the face of climate change.